Metallurgical process



.F iled Feb. 8, 1941 FIG 2 w. E. GREENAWALT METALLURGICAL PROCESS Jan. 5, 1943;

INVENTOR.

, w. E. GREENAWALT Jan.

METALLURGICAL PROCESS I Filed Feb. 8, -194 1 4 Sheets-Sheet 2 FIG. 4

IN VEN TOR.

imam:

Jan. 5, 1943. w. E. GREENAWALT 2,307,459

METALLURGICAL PROCESS Filed Feb. 8, 1941 4 Sheets-Sheet 3 Jan. 5, 1943.

w. E. GREENAWALT METALLURGICAL PROCES 5 Filed Feb. 8, 1941 4 Sheets-Sheet 4 INVENTOR;

FIG 10 ratenteu Jan. 1.3%.)

UNITED STATES PATENT new ,439

rice

18 Claims.

My invention relates in general to metallurgical processes, but is directed more particularly to the treatment of finely divided ore, such as gravity or fioation concentrates, of either ferrous or nonferrous minerals. The object of the process is to simplify the treatment of such ores, to save fuel, and to minimize the dust nuisance, which is an unavoidable accompaniment of the heat treatment of finely divided ores. It is particularly applicable to the smelting of finely divided copper ores in reverberatory furnaces, and to the direct smelting of finely divided iron ore in reverberatoy furnaces, as presenting marked advantages over sintering and blast furnace smelting now in universal use on such ores.

The invention may be applied to either oxidation or reduction. It will be described more particularly to oxidizing roasting and smelting of finely divided copper ore, such as gravity or flotation concentrates, and to non-oxidizing roasting and reverberatory smelting of similar finely divided iron ore or concentrates.

In describing the invention reference may be made to the accompanying drawings in which Fig. 1 is a vertical longitudinal section of the apparatus suitable for carrying out the process and arranged to show the flow of the process. Fig. 2 is the corresponding plan. Fig. 3 is a modified plan. Fig. 4 is a longitudinal section of a modified apparatus for carrying out the process. Fig. 5 is the corresponding plan. Fig. 6 shows, in cross section, the general method of feeding dried ore from the hopper above the roaster shaft into the roaster shaft and showering the ore through the shaft to roast it. Fig. '7 shows a similar arrangement for introducing the hot roasted ore from the roasting furnace into the smelting furnace. Fig. 8 is a detail, in cross section, of the feeding and showering device. Fig. 9 is the corresponding longitudinal section. Fig. 10 is a modification of Fig. 8 in which the ore is charged into the roasting or smelting furnace at its side instead of at the top. Fig. 11 is the corresponding longitudinal section.

Referring to the drawings: I is a shaft roasting furnace, 2 is a dust chamber adjacent the shaft, 3 is an ore drier over the dust' chamber, 4 is an elevator to elevate the fine ore from. the bin 5 to the bin 6, from which the ore is fed, or delivered, to the drier 3, and is advanced, by means of the drier rabbling mechansm, while drying, toward the roaster shaft i. The floor of the drier is heated by the hot gas from the shaft roasting furnace, or by the hot gas from the smelting furnace, or by both combined. The dried ore is delivered from the drier 3, by gravity, into the receiving hoppers I, which are covered with a screen 8 so that lumps in the dried ore, which might give trouble in the ore distributing mechanism over the shaft, are automatically eliminated by the screen. 9 is a reverberatory smelting furnace for smelting the hot roasted ore from the shaft. I0 is a car, or conveyor, to deliver the hot ore from the shaft I into the hopper 21, from which it is distributed, preferably in a shower, into the smelting furnace. i2 is a heat exchanger, either for the purpose of heating water or for heating air by means of the pipes 13, when it is desired to reduce the temperature of the waste smelter gas before introducing it into the roaster shaft through the gas flue M. Any or all of the waste gas from the smelting furnace may be by-passed into the duct chamber through the by-pass flues l5, if it is not desired to pass the smelter ga through the roaster shaft. The settled dust in the dust chamber 2 may be delivered by means of the car, or conveyor, ID, with the hot ore from the roaster shaft, to the smelting furnace.

The arrangement shown in Fig. 3 permits the hot waste gas from the smelting furnace 9 to be conveniently introduced directly into the dust chamber 2 by means of the ducts i5 and the chamber l2; or, indirectly, into the dust chamber 2, by first passing it through the duct l4 and the roaster shaft I. It also permits of a convenient arrangement for a heat exchanger in the chamber l2, and it makes possible the delivery of the hot ore, by means of the conveyor 40, from. the bottom of the roaster shaft l to the hopper 21 over the charge end of the smelting furnace 9, from which it is fed into the smelting furnace, regardless of whether the hot gas from the smelting furnace is introduced directly into the dust chamber 2 or indirectly by first passing it through the roaster shaft I and then into the dust chamber.

The arrangement shown in Figs. 4 and 5 shows the roaster shaft and the dust chamber directly over the smelting furnace. It eliminates the hot ore conveyor, and the hot roasted ore from the shaft and the roaster dust from the dust chamber may be delivered direct, by gravity, from the shaft and from the dust chamber into the smelting furnace. The amount of dust which cannot be so returned will be comparatively small and. can be easily handled in some other way.

The method of introducing finely divided ore from the drier into the hot atmosphere of the shaft roasting furnace and showering it uniformgetting to the rotor.

1y through the shaft, and then introducing the hot roasted ore from the shaft into the smeltin furnace is important. In ordinary flash roasting the finely divided ore is introduced into the shaft with a blast of air, but this involves complications, principally among which is the necessity of some mechanism, such as a ball mill, to grind lumps produced in drying, and the dust produced by the grinding and injecting the dry finely ground ore into the roaster shaft.

The device shown in detail in Figs. 6 to 9, to shower ore through the furnace by introducing it through the furnace roof, and a modification shown in Figs. 10 and 11 to shower the ore through the furnace by introducing the ore at the sides of the furnace, offers a simply way of achieving the desired results. 1 is an ore hopper, preferably with a number of parallel spouts at the bottom, to receive the dried ore from the drier 3. Below the spouts and above the furnace roof, are hollow rotors IS, with blades, mounted on a hollow shaft l7, and journaled in watercooled bearings. At the interior angle of the blades with the rotor, are perforations 29 which permit air or other gas, introduced into the interior of the rotor through the hollow shaft H, to flow into an externally exposed chamber enclosed by the casing [8, which also encloses the rotor. The casing 18 is made removable so that the rotor feeding mechanism may be inspected at any time. The amount of ore fed into the furnace is principally governed by the speed of the rotor and its adjustable proximity to the spout outlet. The rotor and the spouts are so designed in relation to each other that when the rotor stops the How of ore will also stop. To some extent the flow of ore can be roughly regulated by varying the spacing of the hand adjustible plugs 34. The opening in the roof, preferably a slot 28, is made as narrow as practical to permit the ore fed into it by the rotor to pass through without clogging and to prevent an appreciable amount of heat from the furnace getting to the rotor through the slot. Air or other gas passing through the hollow shaft I1, entering the rotor and passing through the perforations 29, is mixed with the descending ore, and the ore and the gas passing through the slot 28 still further tends to prevent an appreciable amount of heat from into the furnace through its top the speed of rotation will usually be slow, and the air is introduced into the hollow shaft H by means of the pipe 30.

Hollow beams [9 still further help to distribute 'the ore and the fresh air in the roaster shaft.

The beams are divided by an internal partition into an upper section 20 for the circulation of air to control the temperature of the beam, and

a lower section 2| open at the bottom through' which gaseous fluid may be introduced into the roaster shaft, as described more fully in my patent, No. 2,108,118, February 15, 1938.

It is preferred to shower the roasted ore direct from the roaster shaft into the smelting furnace, as shown in Fig. 7 by much the same device as that used in showering the dried ore through the roaster shaft, as shown in Fig. 6.

If it is desired to feed and. shower the ore through the sides of the furnace, the feeding and showering device is modified as shown in Figs.

10 and 11. Since, in this case, the temperature of the ignition chamber 36 of the smelting furnace 9 will be quite high, precautions will have to be taken to keep the temperature of the rotor- When the ore is introduced within safe working limits, which can be done by the relative cooling effect of the hot roasted ore continually flowing on it and by the air introduced and mixed with the ore. Fuel, such as fine coke, or coal, may be fed with the ore, and liquid or gaseous fuel may be introduced into the smelting furnace through the rotor I6 and pipes 30.

The operation of the process will now be described as applied to the treatment of copper concentrates, usually flotation concentrates. There are two common types of copper concentrates produced in milling copper ores. One type contains only about the amount of sulphur necessary for the formation of matte for converting; this concentrate may be smelted without roasting and is frequently smelted without drying. Another type, high in sulphur, makes roasting imperative to get the grade of matte desired for smelting; this type is most common. In reverberatory smelting of wet concentrate or cold ore most of the fuel represents unused heat, largely because the heat required to bring the wet and cold concentrate to the smelting temperature, in addition to the large excess of air required in burning the excess fuel which has to-be heated to the smelting temperature, escapes at practically the temperature of the smelter charge, or at from 2000 to 2300 deg. F. In glass furnace smelting the excess heat from the smelting zone is largely used to bring the cold charge to the smelting temperature, and the temperature of the escaping gas is relatively low. This, in reverberatory smelting, is impractical, because the entire charge. has to be kept in a molten state, and the rear-off the furnace, where the gas escapes, is almost-as hot as other parts of the furnace.

It has been estimated that with a calcine charge entering the reverberatory furnace at approximately 500 deg. F. there must be produced in the reverberatory furnace approximately 4,800,000 B. t. u. per ton of charge in order to effect the smelting of the charge. And if the calcines enter the reverberatory furnace at 1200 deg. F. it will require only about 1,900,000 B. t. u. per ton of charge to effect the smelting of the charge. This represents a saving of 2,900,000 B. t. u., or about sixty per cent by charging the ore into the reverberatory at about 1200 deg. F. instead of about 500 deg. F. It also represents a corresponding reduction in the amount of dust produced, due to the greatly diminished draft.

The difference in smelting wet and raw concentrate is considerably greater than this. Wet and raw flotation concentrate usually contains about 10% water, and, with an average atmospheric temperature of 62 deg. F., the difference between 62 and 500 deg. F. is 438 deg. R, which represents a still greater cost for fuel if the concentrate is charged wet and raw,,as compared with charging it dry at a temperature of 500 deg. F., as on the basis of the above estimate.

In addition, the 10% water, or 200 pounds per ton of ore, has to be evaporated, and after it is evaporated the resulting Water vapor has to be brought to the atmospheric temperature of the reverberatory smelting furnace, or about 2800- 3000 deg. F.. without accomplishing any useful results, but which, on the contrary, when taken in connection with the fuel required to generate this useless heat, greatly increases the volume of 'the gas passing through the smelting furnace, and hence, clue to the largely increased draft in the smelting furnace, a corresponding amount of useless dust is produced in smelting which has to be recovered and returned, perhaps repeatedly.

Furthermore, if flotation concentrate is charged wet and raw more sulphur will be oxidized in the smelting furnace than if the ore is charged roasted and hot. One pound of sulphur will, theoretically, require one pound of oxygen for its oxidation to sulphur dioxide, and correspondingly more if some of the sulphur is oxidized to sulphur trioxide. 4.5 pounds of air, or practically, with high efiiciency, 5.0 pounds of air, or 60 cubic feet, are required to produce one pound of oxygen. To oxidize 100 pounds of sulphur per ton of ore in the reverberatory smelting furnace will require at least 500 pounds, 6000 cubic feet, of air. The resulting gas has to be heated to the temperature of the atmosphere of the smelting furnace, or about 2800-3000 deg. F., as also the products of combustion of the carbonaceous fuel necessary to bring the gas to the temperature of the smelting furnace atmosphere. This unnecessary gas, passing through the smelting furnace, unnecessarily increases the draft, which, in turn, unnecessarily increases the dust.

It has been determined by careful research that only about twenty per cent of the heat in reverberatory copper smelting is accounted for in the slag and matte.

The capacity of a reverberatory smelting furname is greatly increased by charging the roasted ore at a temperature of 1200-1400 deg. F. over that of charging the wet and raw ore at an average temperature of 62 deg. F. Drying, heating, and smelting ore in a mass with heat applied from above is one of the most ineflicient of all metallurgical processes. The amount of ore smelted in a reverberatory furnace depends absolutely upon the heat produced and the method of applying it, and a high temperature is the essence of smelting. It is evident that a large amount of useless gas passing through the smelting furnace seriously retards the attainment of high temperatures and that the most effective smelting can be realized by reducing the useless gas to an irreducible minimum. It is true that much of the useless heat is recovered as steam, but the recovery is only partial, inefficient, and relatively troublesome and expensive. The loss of heat is more or less proportional to the amount of gas passing through the furnace. It is desirable to operate the smelting furnace at the highest practical temperature consistent with the economic endurance of the refractories, and to get the highest practical temperature it is necessary to exclude as nearly as practical all useless gas from the smelting furnace.

oxidizing roasting and copper smelting-In operating the process as applied to oxidizing roasting and smelting of flotation concentrate, it is desirable, altho not necessary, to remove the slime from the sand, preferably by wet classification, roasting the sand and smelting the roasted sand with the raw slime, to minimize the dust nuisance in drying, roasting and smelting, as set forth in detail in my Patents No. 2,129,760, September 13, 1938, and No. 2,194,454, March 19, 1940. The amount of slime removed will usually vary from one to five per cent of the ore.

The general arrangement shown in either Fig. 1 or Fig. 4 may be used, depending on the nature of the ore and the probable amount of dust. In Fig. 1 the exhaust gas from the smelting furnace is introduced direct into the shaft or into the roaster dust chamber, and the hot ore from the shaft and the dust fromthe dust chamber is conveyed to the smelting furnace. In Fig. 4 the shaft roasting furnace and the roaster dust chamber are placed directly over the smelting furnace, so that the hot roasted ore from the' roasting furnace and the settled dust from the dust chamber may be delivered by gravity into the smelting furnace. If exhaust smelter gas is passed through the shaft roasting furnace the smelter gas is flowed from the exhaust end of the smelting furnace to the shaft. Ordinarily the arrangement shown in Fig. 4 will be preferred.

The dewatered concentrate is delivered into the receiving bin 5 and is then elevated to the bin 6 and fed to the drier 3, over the dust chamber 2, where it is dried while being stirred and advanced, by means of the drier rabbling mechanism, to the hopper I over the roaster shaft I. The dried ore is then fed in a regulated stream into the shaft and showered through it by means of the rotors l6, and the slots 28 suitably arranged at the top of the shaft, and roasted. The amount of sulphur eliminated will depend upon the original sulphur content of the ore, the height of the roaster shaft, the oxygen in the shaft atmosphere, and the temperature of the roasting. The temperature can be closely controlled, and should be as high as practical without causing fusion difilculties. Ordinarily it will be safe to roast so as to deliver the roasted ore to the smelting furnace at about 1200-1400 deg. F.

If the raw concentrate is low in sulphur the roasting may be done mostly with the heat in the exhaust gas from the smelter, and most of the waste heat from the smelting furnace will be reabsorbed in heating fresh ore preparatory to smelting. If the raw concentrate is high in sulphur the oxidation of the sulphur will ordinarily furnish more than enough heat necessary for roasting. Part of the roaster waste heat can be recovered in the roaster dust chamber, either as hot air which can be used in other operations of th process, or, as preheated water for boilers in connection with the smelting furnace for the production of power. The hot roasted ore falls into the hopper 21 in the bottom of the roasting furnace, and the hot roaster gas flows into a large dust chamber 2 where the dust is settled in hoppers from which it may be delivered, preferably by gravity, as shown in Fig. 4, to the smelting furnace, usually at both sides of the smelting furnace, out of the direct furnace draft. The gas in the dust chamber heats the bottom of the drier in its flow from the roaster shaft inlet to the dust chamber outlet. Air or any other gas may be introduced into or withdrawn from the roaster shaft by means of the hollow beams l9. Almost instantaneous ignition of the ore may be made in the upper part of the roaster shaft by means of a firebox or ignition chamber, such as is shown in detail in Figs. 10 and 11, communicating with the shaft through the opening 22. It is desirable to heat the dried ore as hot as practical, below the ignition point of the sulphides, which will usually be between 400 and 600 deg. F. (204- 316 deg. (2.), to facilitate quick ignition in the roasting furnace. Similarly, it is desirable to have the roasted ore introduced into the smelting furnace as hot as practical without causing fusion difficulties, or usually between 1200-1400 deg. F. (649-760 deg. C.) Instead of charging the hot roasted ore into the smelting furnace as a mass in the usual way, it is preferred to shower it from the roasted hot ore hopper 21 into a vertically enlarged charge end of the smelting furnace, in much the same way as the dried ore is charged into the roasting furnace. The extra height necessary to bring the showered ore to the smelting temperature will have to be determined by practice, and will vary somewhat with the nature of the ore. It will depend mostly on the temperature of the enlarged charge end of the smelting furnace, which will usually be between 2800 and 3000 deg. F. or as high as the furnace refractories will safely and economically stand.

The condition for maintaining a high temperature at the enlarged charge end of the smelting furnace is of some importance. It has been frequently proposed to shower finely divided ore through a shaft roasting furnace, and then flow the ore and the roaster gas direct from the shaft into and through the smelting furnace. Quick and efiicient heating of the showered ore in the smelting furnace becomes impractical under these conditions, because large volumes of useless gas has to be heated to the ordinary atmospheric temperature of the smelting furnace, before efficient smelting can take place, and this becomes more difficult as the atmospheric temperature of the smelting furnace is increased to 2800-3000 deg. F., to almost instantaneously bring the roasted ore at a temperature of 1200-1400 deg. F. to the smelting temperature of about 2100-2300 deg. F. in showering it through the enlarged end of the smelting furnace. This may be illustrated by data gleaned from handbooks on combustion, about as follows:

Temperature of combustion Approximately, also from published data, the combustion of one pound of coal will produce about pounds or 119 cubic feet of gas. Oxidation of the sulphur in roasting or smelting also produces large volumes of gas. It follows, therefore, that the heat can best be increased to a maximum and the dust reduced to a minimum by eliminating, as far as practical, all useless gas from the smelting furnace, and that by so doing the capacity of the smelting furnace can be greatly increased. Higher metal recovery will come with increased smelting temperature.

The hot roasted ore showered through the highly heated enlarged charge end of the smelting furnace is quickly heated to the fusion temperature, or very close to it, and drops on and into the molten bath of the furnace charge in the bottom of the furnace, and is then flowed on or in the molten bath, concurrently with the hot gas from the charge end of the furnace, toward the exhaust end, while in the process of smelting. The molten bath, as in ordinary reverberatory copper smelting, will consist of a layer of matte or metal at the bottom and a layer of slag on top.

All or part of the exhaust smelter gas may be passed through a heat exchanger l2 to recover part of the heat as steam or hot air, or all or part of it may be transferred direct to the roaster shaft I, or to the dust chamber 2 to settle the dust and impart heat to the drier 3. The settled dust is returned to the smelting furnace, preferably direct by gravity as shown in Fig. 4. The dust chamber and the drier are made as long as necessary to effectively dry the ore and settle the dust. The rabbling mechanism of the drier operates slowly to avoid making dust.

If the concentrate is low in sulphur it is desirable to bring it to the roasting temperature, or about 1200-1400 deg. F., with the hot exhaust smelter gas. If the raw concentrate is high in sulphur, the burning of the sulphur will furnish enough heat to sufficiently roast the concentrate for smelting, and little or no exhaust smelter gas would be introduced into the shaft roasting furnace.

If the raw concentrate is subjected to wet classification to separate the slime from the sand, the slime is charged raw and preferably wet, mixed with fuel and flux, compressed if desired, into the smelting furnace and smelted with the roasted sand. The sulphur content of the roasted sand will be somewhat governed by the sulphur content of the slime.

It frequently happens, as in custom plants, that high grade coarse ore has to be smelted with the concentrate; this may be done as shown in Fig. 1, in which 31 may represent an ordinary bin, if the ore does not require roasting; it may represent a blast roasting furnace if the ore requires roasting, as shown and described in detail in my Patent No. 2,152,687, April 4, 1939.

The coarse ore will usually be charged into the smelting furnace at its sides, and, as in present practice, will be smelted by the heat generated at the charge end of the smelting furnace. Dust, loose or agglomerated, and slime, wet or dry, may be charged into the smelting furnace in the same way. So charged the ore will act as fettling to preserve the side walls.

Iron ore roasting and smeZting.-Most low grade iron ores may be concentrated to give a high grade concentrate, and in most instances the highest grade concentrate is obtained by grinding rather fineto 4 to 48 mesh, or even finer. Grinding iron ore wet to a moderate degree of fineness in a ball mill is cheap because iron ore is heavy, usually quite soft, and may be handled in enormous quantities in unit installations. The concentration of finely ground magnetite ores has long been in successful operation, and encouraging progress is being made in concentrating hematite ores by both wet and dry processes.

If the hematite is converted into magnetite for magnetic separation, roasting becomes necessary and the fuel consumed in roasting is an appreciable item of expense. Careful cooling of the roasted ore is necessary. The concentration of the reducingly roasted ore may be made either wet or dry. In either case, under present practice, the concentrate, whether magnetite or hematite, is mixed, wet, with about five per cent of coke, and the mixture containing about ten per cent water, is sintered. The cold sinter, mixed with the necessary amount'of fuel and flux, is smelted in a blast furnace to produce metallic iron. In the treatment of hematite ores by magnetic roasting, this represents three additions of fuel and handling of the ore; one for roasting, one for sintering, and one for smelting. If the ore is magnetite, it represents two separate additions of fuel and handling.

In the present process the concentrate, wet or dry, magnetite or hematite, is passed over the drier to dry it and to heat it. The dried ore is then showered through the shaft roasting furnace in the presence of the hot smelter gas, introduced into the shaft at a temperature of 2000-2500 deg. F., or hotter if practical. Finely ground coal or cake may be added to the ore anywhere before or after drying. Part may be added at the roasting furnace and part at the smelting furnace. The fine coke is preferably added to the wet fine ore at, or before the drier to insure a thorough mixing both for roasting and smelting. Hydrocarbons, such as gas or oil, may be introduced anywhere into the ore stream. The process is continuous, without intermediate handling or cooling.

Pure magnetite, Fe304, melts at 1538 deg. C. (2800 deg. F.). Hematite, F8203, melts at 1565 deg. C. (2849 deg. F.); it sinters at about 1260 deg. C. (2300 deg. F.) The crude iron oxide, as it occurs in iron ore, begins to sinter at about 1000 deg. C. (1832 deg. F.). Metallic iron melts at 1535 deg. C. (2794 deg. F.).

The finely divided iron oxide, showered through the roasting furnace, is quite readily reduced at temperatures ranging from 950 to 1000 deg. C., or as much higher as practical without causing operating diificulties, due to partial fusion. Incipient fusion in roasting is not objectionable, and may be desirable, if the ore particles do not coalesce. Since the oxygen in the Waste smelter gas is practically negligible, the consumption of coal or coke added to the ore before showering it through the roasting furnace, may be strictly controlled by controlling the oxygen in the gas, no matter how much excess of coal or coke there may be.

It will usually be desirable to accumulate a mass of the hot mixture of fine ore and carbon in the bottomof the roasting furnace to give additionaltime for the reducing reactions, and the reducing reactions at a temperature of about 1000 deg. C., are fairly rapid, especially if the hot ore is kept in motion by feeding it from this mass, in a regulated stream, into the smelting furnace. Hydrocarbons, such as gas or vaporized oil, may also be introduced into this hot mov ing mass ore through the hollow beams l9 shown in detail in Fig. 7.

The hot, partly reduced ore, from the roasting furnace is introduced into the highly heated charge end of the reverberatory smelting furnace, where, owing to the intimate mixture of hot finely divided ore and carbon in the highly heated reducing atmosphere maintained by the hydrocarbon burners at the charge end of the smelting furnace, the reduction to metallic iron may be effectively accomplished as the heat is increased from the roasting to the smelting temperature. The metallic iron sinks to the bottom of the furnace; a layer of molten oxide may be above the molten iron; and the slag forms a protecting layer over the molten metal or oxide. There is no probability of either the iron or the oxide being reoxidized in either the roasting or smelting furnace, which has to be carefully guarded against in the ordinary reduction of the iron oxide to metallic iron, without fusion, as in the production of sponge iron.

The reduced molten charge, freed of slag, may be refined in the smelting furnace or transferred to a converter.

The reverberatory smelting unit for iron ore reduction may be as large or larger than blast furnace units. In reverberatory copper smelting, units have reached a capacity of 1500 tons a day, smelting relatively cool ore. The capacity of a reverberatory smelting furnace, charging roasted ore at a temperature of from 1200 to 1500 deg. F., separated from the hot roaster gas, direct from the roasting furnace into the smelting furnace, should at least double the capacity of the same smelting furnace with ore charged at atmospheric temperature, and particularly so if the hot finely divided ore is showered through the highly heated vertically enlarged charge end of the smelting furnace. There will also be a large saving of fuel.

This application is a continuation-in-part of my co-pending application, Serial Number 211,834, filed June 4, 1938, which has matured into Patent Number 2,234,473.

I claim:

1. A metallurgical process comprising, charging finely divided ore concentrate into a smelting furnace to smelt it, passing the hot Waste smelter gas from the smelting furnace into a shaft roasting furnace and from the shaft roasting furnace into i'a dust chamber, drying finely divided ore concentrate with the heat of the hot waste smelter and roaster gas in the dust chamber, showering the dried ore concentrate through the hot waste smelter gas in the shaft roasting furnace to roast it, separating the hot waste smelter gas. from the hot roasted ore con-. centrate in the roaster shaft, and then charging the hot roasted ore concentrate separated from the roaster gas into the smelting furnace to smelt it.

2. A metallurgical process comprising, charging finely divided ore concentrate intoa reverberatory smelting furnace to smelt it, withdrawing the hot waste gas from the'smelting furnace and passing it through a shaft roasting furnace, showering finely divided ore concentrate through the hot waste smelter gas in the roasting furnace to roast it, separating the hot roasted or'e concentrate from the hot roaster gas, and then charging the hot roasted ore separated from the roaster gas into the smelting furnace to smelt it.

3. A process comprising, treating iron ore to produce a finely divided iron ore concentrate, charging the finely divided iron concentrate into the charge end of a reverberatory smelting furnace to smelt it, withdrawing the hot waste smelter gas from the other end of the reverberatory furnace and passing it through a shaft roasting furnace, showering the finely divided iron ore concentrate through the hot waste smelter gas in the roasting furnace to roast it, separating the hot roasted ore concentrate from the hot roaster gas in the roasting furnace, and charging the hot roasted concentrate separated from the roaster gas into the charge end of the reverberatory smelting furnace to smelt it.

4. A process comprising treating ores of metals to produce finely divided sand and slime concentrates, charging the slime concentrate at the side of a reverberatory smelting furnace as a fettling to protect the sides of the furnace, showering the sand concentrate through a vertically enlarged charge end of the reverberatory smelting furnace to give additional time to bring the showered sand concentrate to the smelting temperature, and smelting the sand and the slime concentrate in the smelting furnace.

5. A process comprising treating ores of metals to produce finely divided metal concentrate, showering the finely divided concentrate through the hot atmosphere of a shaft roasting furnace to roast it, separating the hot roaster gas from the hot roasted concentrate in the roaster shaft,

showering the hot roasted concentrate separated from the roaster gas into a reverberatory smelting furnace through restricted openings in its roof to prevent the free flow of gas from one furnace to the other, and smelting the hot roasted concentrate in the smelting furnace.

6. A process comprising showering finely divided metal concentrate through a shaft roasting furnace to roast it, separating the hot roaster gas from the hot roasted concentrate, flowing the hot roasted concentrate separated from the roaster gas in a continuous stream into an externally exposed chamber and from the externally exposed chamber into a smelting furnace, mixing gas with the hot roasted concentrate in the externally exposed chamber, flowing the mixture of hot concentrate and gas into a smelting furnace, and showering the hot roasted concentrate through the highly heated atmosphere of the smelting furnace to smelt it.

7. A process comprising, treating iron ore to produce finely divided iron ore concentrate, charging the iron ore concentrate into the charge end of a reverberatory smelting furnace to smelt it, withdrawing the hot waste smelter gas from the other end of the reverberatory furnace and passing it through a shaft roasting furnace, showering the finely divided iron ore concentrate through the hot waste smelter gas in the roasting furnace to roast it, separating the hot roasted ore concentrate from the hot roaster gas and passing the hot waste roaster gas into a dust chamber to settle the dust and impart heat to a dryer, drying the finely divided iron ore concentrate with the heat of the roaster gas in the dust chamber, and showering the dried concentrate through the shaft roasting furnace to roast it.

8. A process comprising, treating ores of metals to produce finely divided metal concentrate, showering the fine concentrate through a shaft roasting furnace to roast it, separating the hot roaster gas from the hot roasted concentrate in the shaft furnace, injecting fuel through the vertical walls of the charge end of a reverberatory smelting furnace to create a highly heated atmosphere at its charge end, showering the hot roasted fine concentrate separated from the roaster gas vertically downwardly through the highly heated atmosphere of the charge end of the smelting furnace to smelt it, and exhausting the waste smelter gas at the other end of the reverberatory smelting furnace.

9. A process comprising, treating iron ore to produce finely divided iron ore concentrate, smelting the roasted concentrate, passing the hot waste gas from the smelting furnace into a shaft roasting furnace and from the shaft roasting furnace into a dust chamber to settle the dust and impart heat to a drier, drying the concentrate with the heat of the smelter and roaster gas, showering the dried concentrate through the hot smelter gas in the roaster shaft to roast it, and delivering the hot roasted concentrate separated from the roaster gas into the smelting furnace to smelt it.

10. A process comprising, treating ores of metals to produce finely divided metal concentrate, showering the fine concentrate through a shaft roasting furnace to roast it, separating the hot roaster gas from the hot roasted concentrate in the roasting furnace and flowing it into a dust chamber to settle the dust and impart heat to a drier, drying the concentrate with the heat of the roaster gas in the dust chamber, delivering the hot roasted concentrate separated from the roaster gas into the charge end of a reverberatory smelting furnace through its roof, showering the hot roasted concentrate through the hot atmosphere of the charge end of the smelting furnace, and withdrawing the waste smelter gas at the other end.

11. A metallurgical process comprising, delivering finely divided ore into the charge end of a reverberatory smelting furnace to smelt it, exhausting the hot waste smelter gas from the other end of the smelting furnace and passing it through a shaft roasting furnace, showering finely divided ore through the hot waste smelter gas in the shaft roasting furnaceto heat it to a temperature below the smelting temperature of the ore, separating the hot roaster gas from the hot roasted ore, and delivering the hot roasted ore separated from the roaster gas into the charge end of the smelting furnace to smelt it.

12. A metallurgicalprocess comprising, showering finely divided metal concentrate through the hot atmosphere of a shaft roasting furnace to heat it below the smelting temperature of the concentrate, separating the hot roaster gas from the hot roasted ore, showering the hot roasted ore separated from the roaster gas into the highly heated charge end of a reverberatory smelting furnace to smelt it, withdrawing the hot waste smelter gas from the other end of the smelting furnace, and passing the hot waste smelter gas from the smelting furnace through the shaft roasting furnace.

13. A process comprising, treating ores of metals to produce finely divided metal concentrate, showering the concentrate through a shaft roasting furnace to bring it to a temperature below the smelting temperature of the concentrate, separating the hot roasted concentrate from the hot roaster gas, flowing the hot roasted concentrate in subdivided streams into the charge end of a reverberatory smelting furnace through the roof of the charge end of the smelting furnace, showering the hot roasted concentrate through the highly heated atmosphere produced by fuel burners positioned at the charge end of the smelting furnace, and smelting the charge.

14. A metallurgical process comprising, showering finely divided mineral concentrate through the hot atmosphere of a roasting furnace to roast it, separating the hot roasted concentrate from the hot roaster gas, accumulating a mass of the hot roasted concentrate over the charge end of a reverberatory smelting furnace, creating a highly heated atmosphere in the charge end of the reverberatory smelting furnace and exhausting the waste smelter gas at the other end, introducing the hot shower roasted concentrate from the accumulated mass into the charge end of the smelting furnace in a substantially continuous stream and showering it through the highly heated atmosphere of the charge end of the smelting furnace to quickly raise its temperature, and then completing the smelting on the reverberatory smelting furnace hearth.

15. A metallurgical process comprising, showering finely divided ore through a shaft roasting furnace to roast it, separating the hot roaster gas from the hot roasted ore, introducing the hot roasted ore separated from the roaster gas into the charge end of a reverberatory smelting furnace, exhausting the waste smelter gas at the other end, extracting a portion of the heat from the waste smelter gas, and then passing the waste smelter gas through the shaft roasting furnace tto roast the finely divided ore showered through 1 QUV l ,100 I 16. A process comprising, subjecting ores of metals to wet concentration to produce finely divided metal ore concentrate, drying the concentrate, accumulating a mass of the dried concentrate, flowing the dried concentrate in subdivided streams from the dried mass into the highly heated charge end of a reverberatory smelting furnace, showering the dried concentrate of the subdivided streams through the highly heated atmosphere produced by burners positioned at the charge end of the smelting furnace and smelting the charge, exhausting the waste smelter gas from the other end of the reverberatory smelting furnace, and drying the finely divided concentrate with the heat of the waste smelter furnace gas.

17. A process comprising, treating ores of metals to produce finely divided dry metal ore concentrate, accumulating a mass of the dry concentrate, flowing the dried concentrate in continuous subdivided streams from the mass into the highly heated charge end of a reverberatory smelting furnace, showering the dried concentrate of the subdivided streams through the highly heated atmosphere produced by burners positioned at the charge end of the smelting furnace and exhausting the waste smelter gas at the other end, and completing the smelting on the reverberatory hearth.

18. A process comprising, roasting finely divided metal ore concentrate, separating the hot roasted concentrate from the roaster gas, accumulating a mass of the hot roasted concentrate over a vertically enlarged charge end of a reverberatory smelting furnace, creating a. highly heated atmosphere in the vertically enlarged, end of the reverberatory smelting furnace with carbonaceous fuel and exhausting the waste smelter gas at the other end, introducing the hot roasted concentrate into the highly heated vertically enlarged charge end of the smelting furnace in a substantially continuous stream and showering it downwardly across the path of the hot products of combustion of the carbonaceous fuel to quickly raise its temperature, and then completing the smelting on the reverberatory furnace hearth.

WILLIAM E. GREENAWALT. 

